The present invention deals with the provision of cast structures having good hot rollability.
The commercial production of wrought copper base alloys is naturally seriously affected by edge cracking of the alloys during hot rolling or hot working. Silicon-tin bronzes in particular have been found to be susceptible to this edge cracking phenomenon. This is naturally a serious problem commercially. Ternary copper base alloys which contain silicon and tin are even more susceptible to the edge cracking phenomenon, but these ternary alloys are nonetheless desirable for commercial production because they provide a good combination of stress corrosion resistance, high strength and formability.
Various means have been suggested in the art in order to counteract the edge cracking problem, especially in silicon and tin containing copper base alloys. Such means have included both different combinations of elemental additions and ways to vary the hot working process. For example, copper base alloys containing silicon and tin together with mischmetal are taught in U.S. Pat. No. 4,148,633. While this patent does provide improvement in the edge cracking phenomenon, it is naturally desirable to provide even greater improvement and to provide such improvement without the necessity for adding alloying additions. Of further interest is "A Preliminary Assessment of the Value of Minor Alloy Additions in Counteracting the Harmful Effect of Impurities on the Hot Workability of Some Copper Alloys" by R. J. Jackson et al. in the Journal of the Institute of Metals, Volume 98 (1970), Pages 193-198. This article discusses copper alloys which contain impurities such as lead and bismuth. These metals may have their tendencies to crack during hot working reduced by the addition of such materials as thorium, uranium and mischmetal. Other patents of interest include U.S. Pat. Nos. 1,881,257, 1,956,251, German No. 756,035, U.S. Pat. Nos. 2,257,437, 2,062,448 and 3,923,555.
It is, therefore, a principal object of the present invention to provide a method of processing silicon-tin bronzes to provide cast structures having good hot rollability.
it is a still further object of the present invention to provide such a method which yields a copper base alloy which is resistant to edge cracking during hot working.
It is a further object of the present invention to provide a method as aforesaid which does not rely on expensive processing variations or alloying additions.
It is a still further object of the present invention to provide improved cast copper alloys which are resistant to edge cracking during hot rolling.
Further objects and advantages of the present invention will appear from a consideration of the following specification.